It is widely acknowledged that heat is produced during operations of electronic devices such as central processing units (CPUs) of computers. The heat produced must be quickly removed away to ensure the CPUs working normally. Typically, a cooling device such as a heat sink is provided to a CPU for dissipating heat from the CPU. In order to keep the heat sink into close contact with the CPU, a retaining device is generally required.
Up to now, many kinds of retaining devices have been developed. Conventional plate-type of clip was a popular one. The clip generally has a M-shaped configuration, which includes a V-shaped central pressing portion for pressing the heat sink against the CPU and two locking feet depending from the central pressing portion at opposite sides thereof. Each locking foot defines a retaining hole at a free end thereof for engaging with a corresponding catch of a socket connector on which the CPU is installed. An example of this kind of clip is shown in U.S. Pat. No. 6,301,112 B1. In assembly, the locking feet are required to expand outwardly to thereby allow the retaining holes of the locking feet to receive and engage with the catches of the socket connector. It is laborious and difficult to expand the locking feet since the clip has good rigidity. In addition, when large force is applied the locking feet are prone to slide over the catches of the socket connector to damage other electronic devices adjacent the CPU.
Cam-type of clip is another kind of retaining device widely used for mounting of a heat sink. FIG. 8 shows a pair of conventional cam-type clips 90 and a retention module 97. Each clip 90 comprises an integral M-shaped bracket 91 and a cam mechanism 92 pivotably attached to the bracket 91. The bracket 91 has a pair of locking feet 94 integrally formed at opposite ends thereof. Each locking foot 94 has a retaining hole 95 for retaining a corresponding catch 98 of the retention module 97. However, when the clip 90 is combined to the retention module 97, large force is still needed since the bracket 91 is integrally formed and accordingly has a large rigidity.